_"Allison Randal"<http://allisonrandal.com/>: The most basic building blocks of a programming language are its nouns, the chunks of data that get sucked in, pushed around, altered in various ways, and spat out to some new location._

^ Variable Types

Perl 6 (as Perl 5) knows 3 basic types of variables: "Scalars"{link: Scalar} (single values), "Arrays"{link: Array} (ordered and indexed lists of several values) and "Hashes"{link: Hash} (2 column table, with ID and associated value pairs). They can be easily distinguished, because in front of their name is a special character called "sigil"{link: [Perl 6 Lookup Tablet] Sigils} (latin for sign). Its the $ (similar to S) for Scalars, @ (like an a) for Arrays and a % (kv pair icon) for a Hash. They are now invariant (not changing), which means for instance, an array vaiable starts always with an @, even if you just want a slice of the content. The sigils mark also distinct namespaces, meaning: in one "lexical scope"{link: Scoping} you can have 3 different variables named $stuff, @stuff and %stuff. These sigils "can also be used as an operator"{link: [perl 6 lookup tablet] Contextualizers} to enforce a context in which the following data will be seen.

The fourth namespace where you can store and retrieve something under specified names is the one of "subroutines and alike"{link: Callable}, even if you don't might think of them as variables. It's sigil & has to be used only rarely.

Special namespaces of Perl 5 (often marked with special syntax) like tokens (__PACKAGE__), formats, file or dir handle and builtins are now regular (mostly scalar) variables or routines.

Because variables are (as anything in Perl 6) "objects"[Perl 6 OOP Tablet], they have methods. In fact, "any operator"[Perl 6 Operator Tablet], including these square or curly brackets you get specific array and hash values with, are just methods of a variable object with a fancy name.

The primary sigil can be followed by a secondary sigil, called "twigil, which mostly indicate special scope"{link: Twigils } of that variable.

^^ Scalar

This type is known as a storage room for one value, but it's more like a reference that can point to anything: to values of any data type, to _code_, to _objects_ or to a compound of values like a "pair"{link: Pair}, "junction"{link: [perl 6 operator tablet] junctions}, "array"{link: Array}, "hash"{link: Hash} or "capture"{link: Capture}. The scalar context is now called item context hence the _scalar_ instruction from Perl 5 was renamed to "item"{link: [perl 6 lookup tablet] Contextualizers}.

Unlike Perl 5, references are automatically dereferenced to a fitting context. So you could use these $arrayref and $hashref in same way as an array or hash, making $ the variable highlighter, pretty much like in PHP.

^^ Array

is an ordered and indexed list of "scalar variables"{link: Scalar}. If not specified otherwise, they can be changed, prolonged and shorten anytime and used as a list, stack, queue and much more. As in Haskell, lists are processed lazily, which means: the compiler looks only at the part he currently needs. This way Perl 6 can handle infinite lists or do computation on lists that are still building up. The _lazy_ command enforces and the _eager_ command prevents that behaviour on any expression.

The list context is forced with a "@ operator or _list()_ command"{link: [perl 6 lookup tablet] Contextualizers}. That's not autoflattening like in Perl 5 (automatically convert a List of Lists into one List). If you still want that, "say flat(). Or say lol()"{link: [perl 6 lookup tablet] Contextualizers} to explicitly prevent autoflattening.

.pre
@primes # all values as list
@primes.values # same thing
@primes.keys # list of all indices
"@primes[]" # insert all values in a string, uses [] as distinction from mail adresses
$prime = @primes[0]; # get the first prime
$prime = @primes[*-1]; # get the last one
@some = @primes[2..5]; # get several
$cell = @data[1][2]; # get 8, third value of second value (list)
$cell = @data[1;2]; # same thing, shorten syntax
@numbers = @data[1]; # get a copy of the second subarray (6..10)
@copy = @data; # copy the whole AoA, no more reference passing, use binding instead
.pre

^^^ Array Methods

Some of the more important things you can do with lists. All the methods can also used like ops in "elems @rray;"

.pre
? @rray; # boolean context, Bool::True if array has any value in it, even if its a 0
+ @rray; # numeric context, number of elements (like in Perl 5 scalar @a)
@rray.elems; # does the same
@rray.end; # number of the last element, equal to @rray.elems-1
~ @rray; # string context, you get content of all cells, stringified and joined, same as "@primes[]"
@rray.cat; # does the same
@rray.join(''); # also same result, you can put another string as parameter that gets between all values
@rray.unshift; # prepend one value to the array
@rray.shift; # remove the first value and return it
@rray.push; # add one value on the end
@rray.pop; # remove one value from the end and return it
@rray.splice($pos,$n)# remove on $pos $n values and replace them with values that follow that two parameter
@rray.delete(@ind); # delete all cell with indecies of @ind
@rray.exists(@ind); # Bool::True if all indecies of @ind have a value (can be 0 or '')
@rray.pick([$n]); # return $n (default is 1) randomly selected values, without duplication
@rray.roll([$n]); # return $n (default is 1) randomly selected values, duplication possible (like roll dice)
@rray.reverse; # all elements in reversed order
@rray.rotate($n); # returns a list where $n times first item is taken to last position if $n is positive, if negative the other way around
@rray.sort($coderef);# returns a sorted list by a userdefined criteria, default is alphanumerical sorting
@rray.min; # numerical smallest value of that array
@rray.max; # numerical largest value of that array
$a,$b= @rray.minmax; # both at once, like in .sort . min or .max a sorting algorith can be provided
@rray.map($coderef); # high oder map function, runs $coderef with every value as $_ and returns the list or results
@rray.classify($cr); # kind of map, but creates a hash, where keys are the results of $cr and values are from @rray
@rray.grep({$_>1}); # high order grep, returns only these elements that pass a condition ($cr returns something positive)
@rray.first($coder); # kind of grep, return just the first matching value
@rray.zip; # join arrays by picking first element left successively from here and then there
.pre

There is even a whole class of metaoperators that work upon lists.

^^ Hash

is in Perl 6 an unordered list of Pairs. "A Pair"{link: Pair} is a single key => value association and "appears in many places"{link: [Perl 6 Language Design Tablet] Maximum reusage} of the language syntax.

$table = %dev; # same as ~ %dev
%dev.say; # stringified, but only $key and $value are separated by \t
@pairs = %dev; # list of all containing pairs
%dev.pairs # same thing in all context
%dev.elems # same as + %dev or + %dev.pairs
%dev.keys # returns the list with all keys
%dev.values # list of all values
%dev.kv # flat list with key1, value1, key 2 ...
%dev.invert # reverse all key => value relations
%dev.push (@pairs) # inserts a list of pairs, if a key is already present in %dev, both values gets added to an array
.pre

^^ Callable

Internally "subroutines"{link: [Perl 6 Subroutine Tablet]}, "methods"{link: [Perl 6 OOP Tablet]} and "alike"{link: [Perl 6 Lookup tablet] Routine Types} are variables with the sigil _&_ and stored in a fourth namespace. They are no more builtins with an own namespace, that can't be overwritten or augmented with your programming. Of course "scalars"{link: Scalar} can also point to routines.

For a Perl beginner it's enough to know about the everywhere visible, "primary 4 variable types"{link: Variable Types}. But Perl 6 knows about "many more types"{link: [Perl 6 Lookup tablet] object types}, that are organized internally as classes or roles and can be categorized into 3 piles: the undefined, immutable and the mutable types.

^^ Typing

You can explicitly assign one of these types to you scalar, array or hash variable.

> my Int $a;

^^ Pair

are very new and their syntax is used nearly everywhere in the language, where you have associations between a name and a value.

One important difference between a compound structure of lists and hashes and a capture: while "assignments"{link: Assignment} with = the complete content of the named variables will be copied. But not so in the case of a capture. When I change $s in the last example, the content of $cap changes too, because when parameters to a routine are variables, they are also interpolated in the moment the routine is called, not when its defined.

As rightfully expected, assignments are done with the equal sign. But unlike Perl 5 you always get a copy of the right side data, no matter how nested the structure was. You never get in Perl 6 a reference with =. As the only exception may be seen "captures"{link: capture}.

.pre
=
.pre

^^ Binding

Since Perl 6 doesn't know of any references, programmer have to use binding to get 2 variables that point to the same memory location.